The invention relates to a method and apparatus for producing a composite component, and to a composite component produced according to the inventive method.
In a generic method and device, and an associated composite component, disclosed in German patent document DE 100 14 332 C2, a hollow profile is placed into a combination tool containing an internal high pressure forming tool element and an injection molding tool element, and is filled. Thereafter, the hollow profile is formed by the closing movement of the combination tool. Afterwards, an injection molding tool element is activated, in which the necessary cavities are generated by core and pusher movements. The completely formed hollow profile is now encapsulated corresponding to the form of the cavities, and an injection molding element is formed by the curing of the plastics. The composite component is then completed and can be removed from the combination tool after an opening lift.
Such a generation of the cavities by core pulls or pusher movements requires considerable effort, and tends to slow down the production. Moreover, if the pusher movements are carried out with the closed combination tool, only cavities with a very low complexity can be applied, so that the design possibilities of the injection molding element are limited considerably. If the cores are removed with an opened IHU tool, or if the pusher movements are carried out in this state, the production time is increased, which makes the production of the composite component uneconomic.
One object of the present invention is to provide method and apparatus of the type described above, which facilitates the production of a complexly formed composite component, in a simple manner.
This and other objects and advantages are achieved by the method and apparatus according to the invention, in which a hollow profile is widened in a closed combination tool that includes an internal high pressure forming tool element and an injection molding tool element, and is thereby suitable for internal high pressure formation and for local injection molding, by means of internal high pressure before the hollow profile is encapsulated. Additional process monitoring to assure that no hollow profile material enters the two mold parts (upper mold and lower mold or left and right tool half) can therefore be omitted, which reduces the required effort considerably. In addition, the danger of a process disruption is excluded, so that the process safety of the production of the composite component is ensured.
The principal problem of obstruction of the injection molding channels by hollow profile material as it is widened by internal high pressure (which increases if no cover of the injection molding cavities is present during the internal high pressure forming contrary to the known state of the art due to the technical and procedural simplification), is solved according to the invention, because the hollow profile is pressed against the tool contour or engraving only locally in the region of the locations to be encapsulated, while keeping the outlets opening into the tool engraving clear. Such partial abutment of the hollow profile is accomplished by a suitable geometry of the tool engraving of the combination tool, such that, with a forming pressure that is lower than the pressure with which the hollow profile would conform exactly to the contour of the engraving in the region of the parts to be encapsulated (that is, the “calibration pressure”) only a partial abutment of the hollow profile is achieved at the engraving, as the geometry of the engraving does not permit a total abutment with the present forming pressure.
A free space is therefore created between the hollow profile and the engraving, into which injection molding material can be introduced subsequent to the forming with which the local or partial abutment of the hollow profile is achieved.
As the forming pressure is smaller, the localized abutment in question (and or the formation of the free space) can be achieved by a suitable choice of the radii, usually small radii, at the engraving in a simple manner. However, the radii must be designed so as to avoid cutting into the hollow profile due to the pressing at the engraving, which would cause the hollow profile to burst. This means that the edges at the engraving contour limiting the free space should be rounded.
Because the cavity or the free space for injection molding can be designed independently of the state of the art, a larger freedom of design is obtained with the formation of the injection molding elements to be generated. Therefore, more complicated and more complex structures can be achieved in a relatively simple manner during the formation of the composite component. As this is achieved simply by a suitable formation of the contour of the engraving, and no additional pusher movements or core pulls are necessary, the production process is unimpeded and faster.
It is also advantageous that the injection molding tool element and the IHU tool element comprise a common engraving with a widening region, whereby the hollow profile can remain in a single tool during the entire production process without being moved in any manner, thereby avoiding not only added production time, but also additional undesired manufacturing tolerances. Because the encapsulation further extends over the entire widening region or over the section of the hollow profile bulged by means of internal high pressure, a positive fit of the injection-molded element (cured later) with the hollow profile in the axial direction of the hollow profile is achieved, which gives the injection-molded element an undetachable hold on the hollow profile.
In a preferred further embodiment of the device according to the invention, the engraving comprises at least one step-like shoulder in the widening region, against whose edges the widened hollow profile abuts, and which limits the free space with the hollow profile. With the arrangement of shoulders opening into the individual injection molding channels, formings with a higher forming degree can be achieved with a plurality of versions by means of internal high pressure fluid forming without having to forego an encapsulation in this widening region. The hollow profile is bulged by the forming in the encapsulated region, while the injection molding element extends over the bulge region and is formed according to ascending and then descending steps.
In a further development of the invention, the engraving comprises at least one annular groove in the widening region which has a width of 8 mm at the most, and which forms the free space with the widened hollow profile abutting the engraving. The annular groove width thereby depends on the wall thickness and the material of the hollow profile used. In this manner, a composite component can be produced with minimum formation of the hollow profile, while nevertheless obtaining a sufficient axial hold of the injection molding element on the hollow profile by a positive fit. This is advantageous for the use of hollow profile materials which have a small breaking elongation.
The formation of annular grooves only represents a small engagement in the engraving, so that such grooves can be generated in a very simple manner. The groove width is chosen to be so narrow that, during the widening of the hollow profile, the hollow profile material can only prebulge into the grooves so that only small bulges result at the hollow profile, which however assume a rigid positive-fit connection with the injection molding element. Thus, the injection molding channels opening into the annular grooves are not obstructed or blocked by the hollow profile material.
The hollow profile abuts the engraving between the grooves, and thus locally, the grooves being spaced axially from one another in the extending widening region. With the formation of only one annular plant, the abutment of the hollow profile in the widening region is only limited to the edges limiting the groove.
According to a further embodiment of the invention, a composite component can be produced whose hollow profile is bulged in the encapsulated region only to a small extent by the forming and whose injection molding element extends over the bulging region and is formed in the shape of an annular lamella.
In a further preferred embodiment of the device according to the invention, the engraving comprises several annular grooves, whereby at least one groove is formed in the engraving, whose course intersects the course of the annular grooves. By this measure of the engraving design which can be carried out in a simple manner, the composite component can be produced, which comprises several lamella-shaped injection molding elements which are connected to each other by webs. Thus, the individual filigree injection molding elements have a higher stability and rigidity. These longitudinal nuts can proceed in a straight or curved manner, which results in a higher diversity of design possibilities of the webs.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.